Look at the activities listed below. Reason out whether work is done or not done in the light of your understanding of the term 'work'.
(a) Suma is swimming in a pond.
(b) A donkey is carrying a load on its back.
(c) A windmill is lifting water from a well.
(d) A green plant is carrying out photosynthesis.
(e) An engine is pulling a train.
(f) Food grains are getting dried in the sun.
(g) A sailboat is moving due to wind energy.
 

The displacement of the swimmer and the application of a force result in work being done.
(a) Because weight (acting vertically downward) and displacement (acting horizontally) are perpendicular to one another, the donkey is not exerting any effort while carrying the load. But, it does work against friction between its hoofs and the ground.
(c) Work is done as a result of the displacement of water and the force the windmill applies. The work of a windmill is against gravity.
(d) Because there is no displacement, no work is done.
(e) Work is accomplished as a result of the displacement of the train and the force the engine applies.
(f) Because there is no displacement, no work is done.
(g) Work is accomplished as a result of the displacement of the sailboat and the power of the wind.